A cam shaft phase variable device of an engine in which the attachment angle of a crankshaft and a cam shaft is maintained securely without being shifted by disturbance torque. The device has a drive body of revolution having a tubular section and a guide groove of reducing diameter and rotating relatively to the cam shaft and being driven by a crankshaft, a control body of revolution rotating relatively to the drive body through a rotary operating force imparting means and having the outer circumferential surface supported by the inner circumferential surface of the tubular section, an eccentric circular cam rotating synchronously, a movable member for displacing the guide groove, a cam guide intersecting the central axis perpendicularly and displaced by the eccentric circular cam, and an intermediate body of revolution displacing in the direction intersecting the cam guide perpendicularly while being supported on, and rotating integrally with, the camshaft.
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